AnswerJoe,
The first thing that you will want to check is the drive block which is located under the inner tub. Make sure that there is no damage to the drive block which is the most common cause of the clunking noise.

AnswerBill,
In most cases overloading of units is what causes a strain on the coupler but it could also have just broke depending on the age of the unit. Over time the torque from the motor and gearcase can cause undue stress on the coupler which can cause it to break.

AnswerLarry,
Based on the information it does sound like you are on the right track and you will want to clean the oil and put the bolts back in place and install the new clutch and test to see if it works.